[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 34d4c8a [lldb] Have LanguageRuntime and SystemRuntime share a base class (NFC)
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   34d4c8a..1dd39b1  master     -> origin/master
Auto packing the repository for optimum performance. You may also
run "git gc" manually. See "git help gc" for more information.
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 1dd39b1133136c58847d9f2d3c73d2ad8e76e25d.
CMake Error at CMakeLists.txt:3 (cmake_minimum_required):
  CMake 3.13.4 or higher is required.  You are running version 3.7.1


-- Configuring incomplete, errors occurred!